Traditionally automotive brake rotors have been made using cast iron which provides good wear resistance and high temperature properties. However, cast iron is dense relative to other materials so that a cast iron brake rotor is heavy. A heavy brake rotor is undesirable for at least three reasons. First, a heavy brake rotor contributes to the overall weight of a motor vehicle and thus reduces its fuel efficiency and increases its emissions. Secondly, a brake rotor is part of the unsprung vehicle weight, meaning the weight below the springs. Unsprung weight adds to the noise, vibration, and harshness (sometimes referred to as “NVH”) associated with vehicle operation. When unsprung weight is reduced, NVH is usually improved. Thirdly, a brake rotor is a vehicle part that requires rotation during use. Accordingly a heavier brake rotor requires additional energy to increase and decrease rotational speed. Reducing weight of a vehicle rotor also lowers vibration during rotation. Carbon-carbon composites, ceramics, and cermets have also been considered for use in brake rotors but they are expensive and have not achieved widespread adoption as vehicle rotors.
Titanium has been considered as a brake rotor material in Murphy U.S. Pat. No. 5,521,015 and Martino U.S. Pat. No. 5,901,818, incorporated herein by reference. Titanium has excellent strength to weight properties, and it retains strength at high temperatures. However, high costs have heretofore prevented widespread adoption of titanium and its alloys in vehicle brake rotors. Accordingly there still remains a great need for a low cost process for manufacturing titanium brake rotors.
Other brake rotors are shown in U.S. Pat. No. 4,278,153, which discloses a brake disc frictional module composed of sintered metallic material reinforced throughout its entire volume by a grid system of pure metal or metallic alloy. The friction module may be manufactured by sintering the metallic material with the grid reinforcement in either a mold or within the brake disc cup. The internal reinforcement of the frictional module prevents spalling weight loss, friction coefficient decay, or other physical defect as caused by frictional strain during use. The reinforcement material reduces the overall temperature of the disc during use, and aids frictional coefficient of the disc because of the metallic compatibility of the metallic material and grid system.
U.S. Pat. No. 5,620,791 discloses metal and ceramic matrix composite brake rotors comprising an interconnected matrix embedding at least one filler material. In the case of metal matrix composite materials, at least one filler material comprises at least about 26% by volume of the brake rotor for most applications, and at least about 20% by volume for applications involving passenger cars and trucks. In a preferred embodiment of the present invention, the metal matrix composite brake rotor comprises an interconnected metal matrix containing at least about 28% by volume of a particulate filler material and more preferably at least about 30% by volume. Moreover, the composite rotors of the present invention exhibit a maximum operating temperature of at least about 900° F. and preferably at least about 950° F. and even more preferably at least about 975° F. and higher.
U.S. Pat. No. 4,381,942 discloses a process for the production of titanium-based alloy members by powder metallurgy. This process consists of: (a) preparing a titanium or titanium alloy powder having a grain size distribution between 100 and 1000 μm, (b) depositing on said powder a coating of a material such that on contact with the titanium or titanium alloy it forms a liquid phase at a temperature T.sub.1 which is below the allotropic transformation temperature T of the titanium or titanium alloy constituting the said powder, (c) introducing the thus coated powder into a mould, and (d) hot compressing this powder in the mould at a pressure of 10 to 30 MPa at a temperature between T1 and T for a time such that a complete densification of the powder is obtained. This invention has application to the construction of discs for turbines with integrated blades.
U.S. Pat. No. 4,719,074 discloses a metal-ceramic composite article produced by fitting a projection formed on a ceramic member into a hole formed in a metallic member having a hardened region and an unhardened region on its surface such that the ceramic member is monolithically bonded to the metallic member and the deformed region of the metallic member resulting from the fitting is located within its unhardened range, has a high bonding force between the ceramic member and the metallic member and is adapted to be used in engine parts, such as turbocharger rotor, gas turbine rotor and the like, and other structural parts exposed to high temperature or to repeating loads, by utilizing the heat resistance, wear resistance and high strength of the ceramic.
U.S. Pat. No. 5,053,192 discloses deforming combustion products by extrusion at an extrusion temperature chosen in the range from 0.3 T1 to T2, wherein T1 is the melting point of a hard phase of the combustion products and T2 is the melting point of a binder material in a container (5) made up of vertically extending segments (12) defining spaces (13) with one another and having a die (14) and a heat insulated sizing member (17) the temperature conditions of extrusion being controlled by means of a unit (21) having a temperature pick-up (22) and a member (23) receiving information from the pick-up (22) and sending a command for moving the punch (10).
U.S. Pat. No. 5,139,720 discloses manufacturing a sintered ceramic material using the heat generated in a thermit reaction as a heating source, a pre-heating is applied preceding to the sintering step or a mixture comprising: (A) at least one ceramic powder, (B) at least one non-metallic powder selected from the group consisting of carbon, boron and silicon, and (C) a metal powder and/or a non-metallic powder other than the above-mentioned (B) is used. Homogeneous and dense sintered ceramic material or sintered composite ceramic material can be obtained by this method, and the fine texture thereof, and the phase constitution, the phase distribution and the like of the composite ceramic phase can be controlled sufficiently.
U.S. Pat. No. 5,701,943 discloses a metal matrix composite made by blending non-metal reinforcement powder with powder of metal or metal alloy matrix material, heating to a temperature high enough to cause melting of the matrix metal/alloy and subjecting the mixture to high pressure in a die press before solidification occurs.
A principal advantage of the present invention is that it enables, for example, titanium brake rotors to be manufactured at a relatively low cost. The invention also provides, for example, titanium brake rotors at substantially lower cost than prior art carbon-carbon composite brake rotors. Other advantages of the invention will become readily apparent to persons skilled in the art from the following specification and claims.